1. Field of the Invention
The present invention relates to a valve operation control system in an internal combustion engine, comprising an engine valve openably and closably supported on an engine body, a valve spring for biasing the engine valve in a valve-closing direction, and valve driving means interposed between a valve-operating cam and the engine valve to transmit a force in the valve-opening direction provided by the valve operating cam to the engine valve.
2. Description of the Prior Art
There is already knoWn, from Japanese Utility Model Application Laid-open No. 52111/84 or the like, a valve operation control system Which provides controlling of opening and closing an intake valve or an exhaust valve as an engine valve not only by the coaction of a valve-operating cam and a valve spring but also by the operation of an electromagnetic actuator depending upon the operational state of an engine.
The present applicant has proposed an engine valve-opening and -closing operation control system of the type described above (Japanese patent Application No. 123647/87) in which an attractive force of an electromagnetic actuator is utilized at a maximum to provide an improvement in performance of an engine. However, the system is accompanied by a problem that a valve-closing timing can be controlled, but it is impossible to provide a variable control of valve-opening timing where an inertial supercharging can be put to practical use, because the engine valve is opened by excitation of the electromagnetic actuator and closed by a spring force as a result of releasing of such excitation.